We have realised that there are various shortcomings in the function and efficiency of known methods of securing a cover of a catheter clamp in a clamping condition.
Broadly, known catheter clamps comprise two (plastic) components, a base and a cover/lid, hinged together such that when in an open condition, a catheter can be fed through the base and the base adhesively attached to a patient's skin around an insertion site in the skin. The cover is manually pivotable to grip the catheter and a retaining clip arrangement is operative to retain the cover in a clamped condition.
The retaining clip arrangement typically comprises two lugs which form a resilient part of the cover. As the cover approaches the clamped condition, the lugs are deflected by aperture-defining surfaces in the base. When the lugs have passed through the apertures, the lugs spring back and locate under the edges of the apertures. To release the retaining clip arrangement, the cover is lifted away from the base forcing the lugs out of the apertures.
One known catheter clamp comprises a feature whereby when in the clamped position co-operative faces on the cover and the base are forced together and held by a retaining clip arrangement to form a barrier to the ingress of infectious material. Also, the force required to compress the catheter into a close-fitting pathway of the base is held by the retaining clip. Both of those forces act against the retaining force of the clip, reducing the force required to release the clip.
In practice this undesirable balance of forces is difficult to maintain. Small dimensional variations in the plastic components, such as the size and position of pivot pins, pivot pin locations, co-operative faces of the cover and the base, as well as co-operative features of the clip, can build up and cause significant variation in the retain/release force. Also, the characteristics of the design means that a small variation in mould quality, such as the amount of rounding on the aperture edge and/or on the lugs, as well as flash from the moulding process inhibiting the amount of clip engagement, will cause further variation in the retain/release force. Furthermore, as the catheter clamp has to secure catheters from different manufacturers, variability in the diameters and compression strength of those catheters will also contribute to inconsistency in the retain/release force of the clip.
The sensitivity of the retaining force reduces the effectiveness of the catheter clamp. When the retaining force is low, the grip on the catheter is reduced. Also, a low retaining force reduces the force between co-opting faces and reduces the effectiveness of the bacteriological barrier. Furthermore, a low retaining force increases the risk of accidental release. However, when the retaining force is too strong then it is difficult to release the cover.
Because the clamp is released by forcing the cover away from the base, it is necessary to use two hands with one finger of one hand lifting the cover, whilst a finger from the other hand restrains the base from pulling away from the patient's skin. Because the clamps are small this can be an awkward operation.
Furthermore, because of the release method, it is necessary to provide a feature by which the cover can be lifted, and it is then susceptible to be accidentally caught in bedclothes, for example, which can cause the clamp to become released from the clamped condition.
The cover comprises two separate lugs spaced to each side of the catheter, and set apart at a distance to provide an even pressure on the co-operative sealing faces. However, in operation the cover can twist as the force is applied to operate the clamp and so only a single part of the clip is engaged, thus reducing the effectiveness of catheter clamping. This partial engagement would not be obvious to the user. Failure to fully engage both sides of the clip can reduce the grip on the catheter by up to fifty percent and cause the co-operative sealing faces not to come together.
We seek to provide an improved catheter clamp.